The invention relates generally to continuous casting.
More particularly, the invention relates to a continuous casting method and a continuous casting apparatus, especially a method of and an apparatus for continuously casting metals, e.g., steel.
In the continuous casting of steel, a stream of molten steel is continuously admitted into a first end of a casting passage defined by a continuous casting mold. The mold is cooled, and the molten steel adjacent to the walls of the mold solidifies to form a thin shell of solidified steel. The steel which is not immediately adjacent to the walls of the mold remains in the molten state and is confined within the solidified shell. The shell and its molten core together constitute a continuously cast strand.
The strand is continuously withdrawn from the mold via a second end of the casting passage. Outside of the mold, the strand is subjected to secondary cooling by water sprays in order to solidify the molten core.
The strand shell is in full contact with the mold at the trailing end of the strand, that is, at the location of the mold where solidification begins. Downstream of this location, the shell contracts from the mold due to the shrinkage which accompanies solidification and cooling. Consequently, a small air gap is present between the strand and the mold downstream of the trailing end of the strand.
The trailing end of the strand tends to stick to the mold. This condition is undesirable because the thin shell will tear under the action of the withdrawal force thereby resulting in poor surface quality or a breakout, i.e., an escape of the molten core. In order to prevent the shell from sticking to the mold, it has thus become the practice to oscillate or reciprocate the mold during casting.
While mold oscillation is effective in preventing sticking of the shell to the mold, a relatively expensive and complicated mechanism is required to oscillate the mold. Furthermore, undesirable oscillation marks are formed on the surface of the strand.